Camshaft phasers for varying the phase relationship between the crankshaft and a camshaft of an internal combustion engine are well known. A prior art vane-type phaser generally comprises a plurality of outwardly-extending vanes on a rotor interspersed with a plurality of inwardly-extending lobes on a stator, forming alternating advance and retard chambers between the vanes and lobes. Engine oil is supplied via a multiport oil control valve (OCV), in accordance with an engine control module, to either the advance or retard chambers as required to meet current or anticipated engine operating conditions.
In a typical prior art vane-type cam phaser, a locking pin, disengage-able by oil pressure, is slidingly disposed in a bore in a rotor vane to permit rotational locking of the rotor to the stator (or sprocket wheel or pulley) under certain conditions of operation of the phaser and engine. In older prior art phasers, it is desired that the rotor be locked at its parked position at an extreme of the rotor authority, either at the full retard position as in the case of an intake camshaft phaser or at the full advance position as in the case of an exhaust camshaft phaser. To assist in positioning the rotor for lock pin engagement, it is known to incorporate a mechanical stop for the rotor and a torsional bias spring acting between the rotor and the stator to urge the rotor against the stop for locking.
In newer prior art phasers as disclosed in co-pending application having Ser. No. 11/225,772, it is desirable that the rotor be lockable to the stator at an intermediate position, preferably within an increased rotor range of rotational authority. A known problem in such phasers is that there is no mechanical means such as a stop to assist in positioning the rotor for locking in an intermediate position; thus, locking is not reliable, and an unacceptably high rate of locking failures may occur.
Further, in prior art phasers, the torsion spring may generate an unwanted torque on the rotor about an axis orthogonal to the rotor axis, causing the rotor to become slightly cocked within the stator chamber before the phaser is installed onto the end of a camshaft during engine assembly. This cocking is permitted by necessary clearances between the rotor and the stator. Although relatively slight, such cocking can be large enough to prohibit entry of the camshaft into the rotor during engine assembly.
What is needed in the art is an improved vane-type camshaft phaser having additional range of rotational authority wherein the rotor may be reliably locked to the stator at an intermediate position within the range of authority.
What is further needed in the art is an improved vane-type camshaft phaser wherein the rotor of an assembled phaser may be reliably entered onto the end of a camshaft during engine assembly.
It is a principal object of the present invention to cause a rotor lock pin to be properly positioned for engagement with a stator.
It is a further object of the present invention to increase the reliability of entry of the rotor of an assembled phaser onto an engine camshaft during engine assembly.